1. Field of the Invention
The present invention relates to a method of and an apparatus for manufacturing a cathode-ray tube.
2. Description of the Related Art
The phosphor screens of color cathode-ray tubes usually comprise a color phosphor screen of the so-called black matrix type which includes a black pattern serving as light absorbing films interposed between phosphor stripes (or dots) of red, green, and blue, for example. A metal back layer comprising an aluminum film, for example, is disposed on the color phosphor screen. A conductive carbon film for applying a high voltage to the metal back layer is coated between the metal back layer and panel pins of metal which support color selection electrodes on the inner surface of the facepanel. The high voltage is applied successively to an anode button, a conductive film within the cathode-ray tube funnel, contacts extending from the color selection electrodes, the color selection electrodes, the panel pins, the conductive carbon film, and the metal back layer.
One conventional process of manufacturing a color cathode-ray tube having such a color phosphor screen is shown in FIG. 1 of the accompanying drawings.
The inner surface of the facepanel of a cathode-ray tube is coated with a photosensitive film of PVA (polyvinyl alcohol), PVP (polyvinyl pyrrolidone), or the like. After the coated photosensitive film is dried, it is exposed to ultraviolet radiation using color selection electrodes as an optical mask and then developed with water or the like, forming stripes (or dots) of a resist layer in positions corresponding to respective colors. Then, the entire surface formed so far including the resist layer is coated with a carbon slurry. After the coated carbon slurry is dried, a reversal development process is carried out. That is, a reversal agent such as of H.sub.2 O.sub.2 or the like is introduced to well the resist layer, and the resist layer and the carbon layer thereon are lifted off as by water washing or the like, thus forming carbon films serving as light absorbing films in a step 1.
Then, a green phosphor slurry is coated. After the coated green phosphor slurry is dried, it is exposed through the color selection electrodes, and then developed to form a green phosphor layer (phosphor stripes or dots) between predetermined carbon films in a step 2.
Thereafter, the panel pins are cleaned to remove any unwanted phosphor layer attached thereto in a step 3. The panel pins may be cleaned by applying a shower of water to the panel pins, immersing the panel pins in a chemical solution such as of ammonium fluoride or the like (so-called rinsing process), or physically scraping any unwanted phosphor layer off the panel pins with a rotating sponge or brush while water is being supplied (so-called trimming process).
Subsequently, a blue phosphor layer is formed in a step 4, and the panel pins are cleaned in a step 5. Similarly, a red phosphor layer is formed in a step 6, and the panel pins are cleaned in a step 7. A color phosphor screen is now completed.
Then, in preparation for forming a metal back layer, an intermediate film for providing a flat surface is coated on the color phosphor screen in a step 8. Thereafter, a metal back layer comprising an aluminum film is formed on the intermediate film in a step 9.
The panel pins are then coated with a conductive carbon film which electrically connects the panel pins and the metal back layer in a step 10.
Thereafter, with the color selection electrodes mounted on the panel pins, the facepanel is sealed to the cathode-ray tube funnel with frit in a step 11.
According to the conventional process of manufacturing a color cathode-ray tube as shown in FIG. 1, the cleaning steps 3, 5, 7 are carried out to remove any unwanted phosphor layer from the panel pins after the respective phosphor layers of the colors are formed.
It has been found out that after the phosphor screen is completed, debris is produced when panel pins are scraped upon attachment and detachment of color selection electrodes, and an unwanted conductive carbon layer attached to panel pins subsequently falls as debris, causing a reduction in the ability of the cathode-ray tube to withstand the high voltage.
If the panel pins are cleaned by immersing them in a solution of ammonium fluoride, then not all phosphor particles attached to the panel pins can be removed. If the panel pins are cleaned by physically scraping phosphor particles off the panel pins with a rotating brush or the like, then the panel pins have to be cleaned one at a time because of a limitation posed by the layout of the cleaning equipment, and it takes time to clean four guide pins, resulting in poor index. Furthermore, since the cleaning process requires the panel pins to be processed with water, it is difficult to clean a plurality of panel pins, e.g., four panel pins, at the same time due to mechanism complexities, and the cleaning process using water poses the problem of water splashes.